Pressurized gas-operated circuit breaker with load interrupter and isolator contact means



April 26, 1966 K. HOLZINGER 3,248,507

PRESSURIZED GAS OPERATED CIRCUIT BREAKER WITH LOAD INTERRUPTER ANDISOLATOR CONTACT MEANS Filed July so; 1963 5 Sheets-Sheet 1 ill INVENTORKcwL Holzm er ATTORNEYS Apnl 26, 1966 K. HOLZINGER 3,248,507

PRESSURIZED GAS OPERATED CIRCUIT BREAKER WITH LOAD INTERRUPTER ANDISOLATOR CONTACT MEANS Filed July 30, 1963 5 Sheets-Sheet 2 Q -1 7Q N m0 m N 3 H W P M INVENTOR BY Karl, HOLZ/Hger 4 Q A PM 69W & ATTORNEYSAprifi 26, 1966 K. HOLZINGER 3,248,507

PRESSURIZED GAS OPERATED CIRCUIT BREAKER WITH LOAD INTERRUPTER ANDISOLATOR CONTACT MEANS 5 Sheets-Sheet 5 Filed July 30, 1963 ZNVENTOR duhUnited States Patent 3,248,507 PRESSURIZED GAS-OPERATED CIRCUIT BREAK-ER WITH LOAD INTERRUPTER AND ISOLATOR CONTACT MEANS Karl Holzinger,Nussbaumen, Aargau, Switzerland, assignor to Aktiengesellschaft Brown,Boveri & Cie., Baden, Switzerland, a joint-stock company Filed July 30,1963, Ser. No. 298,740 Claims priority, application Sweden, Aug. 7,1962, 9,411/62 4 Claims. (Cl. 200-448) This invention relates to apressurized gas circuit breaker, with multiple interruption, in whichseveral impulse-operated interrupting contacts and at least one set ofisolating contacts, the latter being open in the switchedout position ofthe circuit breaker, are connected in series, the interrupting contactsbeing arranged in pairs within the twin interrupter chambers, at leastone pair of said chambersbeing mounted on an insulator column, while theisolating contacts, situated in the isolator chambers, are supported bya separate insulator column.

The continually increasing demands on the switching capacity of circuitbreakers have led to the use of interrupting contacts, which perform theactual interruption, in conjunction with isolating contacts, whichmaintain the interruption in the switched-out position.

- The interrupting and isolating contacts are connected in series. Atthe same time both types of contacts must operate in such a manner thatthe isolating contacts are opened after the interrupting contacts, assoon as the flow of current in the latter has ceased. The isolatingcontacts when opened provide suflicient insulation to allow theinterrupting contacts to be closed again. For a predetermined operatingvoltage a definite number of isolating contacts are required, dependingon their formation, while the number of necessary interrupting contactscan vary as a function of the current to be interrupted. In order toachieve, within a definite rated voltage, a suitable construction'of aseries of circuit breakers, graded according to the current to beinterrupted, it has been proposed that the interrupting contacts bearranged in pairs in twin interrupter chambers and that these chambersbe mounted on an insulator column. The isolating contacts are similarlysituated within the isolator chambers which are mounted on a separateinsulator column. Thus, the extinguishing medium is led to both sets ofcontacts at the same time. It has been shown, however, that such abreaker had a relatively long extinguishing period whereby as a resultof the ever increasing growth of short-circuit currents in large highvoltage networks it was no longer possible to hold the effect of theshort circuits on the various equipment in the circuit sufiicientlysmall.

In order on the one hand to shorten the time of interruption of thebreaker and on the other hand to arrive at a simple constructional form,it is proposed in this invention that the insulator column which carriesthe isolating contacts should consist of an operating valve situated atits base, a supporting, insulator which con.-

tains a channel through which the pressurized gas flows to operate thecontacts and the approximately horizontal isolator chambers arranged atthe top of the supporting insulator. The isolator chambers areconstantly under gas pressure and communicate with an elongatedcompressed gas tank, on which all three insulator columns upstand,through at least one of the insulator columns supporting theinterrupting contacts, said insulator columns having a pneumaticoperating mechanism situated at their base connected through aninsulating-rod to the operating valves situated in the interrupterchambers.

Examples of apparatus for carrying out the ideas behind this inventionare shown in the accompanying drawings:

FIG. 1 shows an example of the construction of one pole of a circuitbreaker within all three insulator columns.

FIG. 2 illustrates a further example of the construction of one pole ofa circuit breaker also with three insulator columns.

FIG. 3 shows on a larger scale closer details of the control equipmentof a circuit breaker according to the invention.

With reference now to FIG. 1, which illustrates one pole of a multi-polecircuit breaker, numeral 1 indicates an elongated tank containing apressurized gas on the middle of which the insulator column 2 upstands.This column comprises an operating valve 2a 'afiixed to the base, thetwo-part hollow supporting insulator 2b and the two isolator chambers 20in which the isolating contacts are contained. The supporting insulator2b 0011-.- tains the channel 2d for the gas which actuates the isolatingcontacts in the isolator chamber 2c by means of the operating valve 2a.Upstanding upon each end of the gas tank 1 is an insulator column 3which has a pneumatic operating mechanism 3a at its base and which alsosupports, on a multiple-part supporting insulator, the twin interrupterchambers 3c, in which the interrupting contacts (not shown in thefigure) are arranged in pairs. The supporting insulators 3b are alsohollow and contain the insulated rod 3d, which connects, in the usualWay, the pneumatic operating mechanism 3a with the operating valves (notshown) which are mounted in the twin interrupter chambers 3c. The curvedpipe 3e connects the interior of the supporting insulator 3bpneumatically with the gas tank 1. The gas line 4 connects the isolatorchambers 20 to the gas tank 1 through the center of the supportinginsulator 3b. A non-return valve can be built into the gas line 4 whichprevents a flow-back of the pressurized gas from 26 to 3b. Theinterrupting contacts, situated in the twin interrupter chambers 30, andthe isolating contacts, in the isolator chambers 20, are connected inseries between the external electrical terminals 5 and 6. The primarycircuit of the current transformer 7 is connected between the lower twininterrupter chamber of the insulator column 3 on the left and theleft-hand-side isolator chamber of the insulator column 2. Thetransformer 7 is thus situated in the immediate vicinity of theleft-hand-side insulator column 3 thus attaining the optimumspace-saving arrangement. Item 8 is the control block which is connectedon one side through the pneumatic line 9 with the operating valve 2a ofthe insulator column 2 and on the other side through the electricalconductor 10 with the operating mechanism 3a of the insulator column 3.The arrangement as shown in FIG. 1 is particularly suitable when theterminals 5, 6 of the breaker are required on the top of the breakerpole.

The arrangement as shown in FIG. 2 is somewhat different and isespecially advantageous when, because of the layout of the conductors inthe installation, it is desired that the terminals 5, 6 of the breakerbeplaced at a relatively lower level, i.e., at somewhat the same level asthe lower twin interrupter chambers 30. In

this case an isolator 11 can be situated in the immcdiate vicinity ofthe current transformer 7, thus saving space, and both the terminals 5and 12 lie at approximately the same level. The isolator chambers 20 arethen situated at the same level as the twin interrupter Patented Apr.26, 1966 FIG. 3 shows in enlarged dimensions the closer details of thecontrol of the insulator columns. On the left-hand side of the gas tank1 a portion of the insulator column 3, which carries the interrupterchambers 30 (FIG. 1) is shown. At the foot of this insulator column thepneumatic operating mechanism 3a is situated and this consists of apiston 3f placed in the housing 3g. The piston 3 is connected to theoperating valves (not shown in the figure) in the twin interrupterchambers by the insulated rod 3d, which itself is situated in the centerof the supporting insulator 3b. This supporting insulator 3b ispermanently connected to the gas tank 1 through the bent tube 3e. 3h isa preliminary valve which is connected to the armature 3k of the magnet31 by the valve rod 31'. The magnet 31 is a permanent magnet and also isprovided with a winding 3111. The left end of the valve rod Si isconnected to the resetting piston 3n against which the spring 30 acts,the springbeing placed in the space to the left of the piston 311. Thisspace is connected to the space under the piston 31 by the hole 3p. Thehole 3p can also be constructed as an adjustable orifice in the usualway. The gas line 3g is also connected to this space while the gas line3r is connected to the space at the right of the resetting piston 311.The operating space of the preliminary valve 3h is permanently connectedto the gas container 1 by the tube 3s. A similar insulator column 3 issymmetrically placed at the right-hand side of the gas tank 1. For thesake of clarity this insulator column has been omitted in the figure.The insulator column 2, which carries the isolator chambers 20 (FIG. 1),contains at its foot an operating valve 2a which is connected to the gastank 1 by the supports 2] whereby the exit side opens through the tube2g into the channel 2d of the insulator column 2b. The valve plate 2h isconnected to the piston 2k by the valve rod 21', said piston 2k beingcontained in the housing 21 to which the line 9 is connected, which inturn leads to the pneumatic exit side of the control block 8. Thecontrol block 8 consists of the switch-out valve 8a with its associatedspring operator 8b and its trip releaser 80 as well as the switch-invalve 8d with its associated spring operator 8e and its trip releaser 8The valves 8a, 8d are constructed in the usual way as servo valves, theinlet side of the valve 8a being connected to the gas tank 1 by the tube8g while the outlet side of the valve 8d is connected to the operatingvalve 2a by the gas line 9. The outlet side of the valve 8d is alsoconnected to the gas line 3r through the intermediate switch of theimpulse valve 8/1 which consists of a through-bored valve body 81' and areloading spring 8k whereby the latter is mounted between 8i and thehousing. The space above the driving piston of the switch-out valve 8ais connected to the gas line 3q through the non-return valve 81. Each ofthe spring operator release mechanisms 8b, 8e has a cam 8m, 8n, which ismounted on the shaft 80, the shaft itself being connected through thelinkage Sp to the pneumatically operated spring loaded mechanism Sq. Theincoming electrical conductor 10a is joined to both the winding 3m ofthe tripping magnet 31 by the conductor 10 and the tripping magnet 80 bythe conductor 10b.

The operating principle of the arrangement described is as follows:

To trip the breaker an electrical impulse is applied through theconductors 10a, 10, 10b to the tripping magnets 31 and 8c. In this waythe field of the tripping magnet 31 is weakened to such an extent'thatthe pressure acting on the valve plate of the preliminary valve 3h opensthis valve against the force of the spring 30 and thus releases thearmature 3k of the magnet. The pressurized gas flows under the piston 3fforcing it together with the rod 3d upwards thereby causing, in theusual manner, the operating valves 32, situated in the twin interrupterchambers 30 (FIG. 3), to open the interrupting contacts. The trippingmagnet 8c which also serves to switch off the operating current, issimultaneously activated. Thus, the spring operator release mechanism,which is constructed as a knuckle-joint, unlatches and the switch-outvalve 8a opens. The pressurized gas flows from the gas tank 1 throughthe pipe 8g, the valve 8a and the valves 8a, which as a result of itsdifferential-piston method of construction opens permitting the gas toflow through the gas line 9, and against the driving piston 2k of theoperating valve 2a. This valve opens permitting the pressurized gas fromthe tank 1 to flow through the tube 2g into the channel 2d of thesupporting insulator 2b, thus opening, in the usual manner, theisolating contacts situated in the isolator chambers 20 (FIG. 1). Thenecessary delay between the opening of the isolating contacts after theopening of the interrupting contacts is advantageously achievedaccording to the invention because as a result of the electricaltransmission of the tripping impulse to the insulator column 3 and therapid mechanical transmission within the supporting insulator 3b thedesired time-lead is given to the interrupting contacts.

As soon as pressure is present in the tube 2g the pneumatic mechanism 8gis operated to rotate shaft and the spring operator 8b-is reset throughthe linkage 8b, the shaft 80 and the cam 8m.

The closing operation is brought about by applying an impulse to theclosing magnet 8 whereby the spring operator 8e unlatches and the valve8d opens so that the gas line 9 is exhausted and the operating valve 2ais closed. The isolating contacts then close in the usual manner and thebreaker is thus closed since the interrupting contacts had been openedonly for a short period during the switching out process.

In the event of a fault arising in the conductor 10, for example, asevered wire, or if the tripping magnet 3l fails to operate, theinterrupting contacts would not be able to operate after the order hasbeen given so that the isolating contacts must undertake the function ofinterrupting the current, a task which they are not capable ofperforming, and they will consequently be damaged. In order to preventthis, the invention provides that for such cases use is made of theelectrical conductor 10 or the pneumatic circuit which consists of theimpulse valve 8h and the gas line 3r. As can easily be seen in FIG. 3,the gas lines Sr and 9 are simultaneously subjected to pressure at thetime the breaker is tripped. Thus, the pressurized gas acts on theright-hand surface of the piston 3n so that the valve 3h will in thisway be forced open consequently opening the interrupting contacts. Theimpulse valve 8h closes the pressurized gas source to the gas line 3rshortly after thus exhausting it. For this purpose the body of the valveSi is constructed as a through-bored, self-holding differential pistonso that 81 remains in the closed position as long as pressure ismaintained on the gas line 9 side of the piston. As soon, however, asthis pressure is removed, for example, by closing the breaker, the bodyof the valve Si is returned by means of the spring 8k as shown in thefigure. A further failure could occur if the tripping magnet 80 failedto operate. The interrupting contacts of the column 3 would operatenormally but the isolating contacts of column 2, after the order toswitch out has been given, would not open so that the breaker, throughits interrupting contacts, is switched out only for a short period andcannot be maintained in the open position. In order to prevent this, theinvention provides the gas line 3q as a pneumatic transmitting means.When the interrupting contacts are opened the gas line 3g is subjectedto pressure as soon as the valve 311 has opened. Thus, the pressurizedgas, through the non-return valve 81 acts behind the driving piston ofthe switch-out valve 8a Opening it thereby causing the isolatingcontacts to open in a similar manner to that described above.

The novel arrangement is not restricted to the examples described above.In certain instances it can sufiice that the breaker pole consist ofonly one insulator column 3 while the insulator column 2, for example,contains only one isolator chamber. As a variation of FIG. 3, the

tripping mechanisms 80 and 31 can also be connected in contact meanswithin said interrupter chamber, an operating valve at said interrupterchamber controlling admission of pressurized gas into said chamber fromthe interior of said insulator column to actuate said contact means, avalve rod extending upwardly through said insulator column from the basethereof for actuating said operating valve, electro-responsive controlvalve means, pneumatically actuated drive means connected to said valverod at the base of said insulator column and which are controlled bysaid control valve means, a second hollow insulator column upstanding onsaid gas supply tank, an isolator chamber located at the upper end ofand in communication with the interior of said second insulator column,pressure gas operated isolator contact means within said isolatorchamber, conduit means connecting the interior of said isolator chamberwith the interior of said gas supply tank, a pneumo-responsive controlvalve means located at the base of said second insulator column forcontrolling flow of pressurized gas from said gas supply tank to saidisolator contact means for actuation thereof, circuit means connectingsaid load interrupter contact means and said isolator contact means inseries between inlet and outlet terminals of said circuit breaker, acontrol block on said gas supply tank, electrical transmission meansextending from said control block to said electroresponsive controlvalve means at said first insulator column, pneumatic transmission meansextending from said control block to said pneumo-responsive controlvalve means at said second insulator column and auxiliary pneumatictransmission means extending from said pneumatic transmission means atsaid control block to and for actuating auxiliary pneumo-responsivemeans at said normally electro-responsive control valve means to actuatethe latter in the event of a failure of the normally operativeelectroresponsive means.

2. In a pressurized gas operated circuit breaker, the combinationcomprising an elongated tank containing a supply of pressurized gas, afirst hollow insulator column upstanding on said gas supply tank andhaving its interior in communication with the interior of said gassupply tank, an interrupter chamber located at the upper end of saidinsulator column, pressure gas operated load interrupter contact meanswithin said interrupter chamber, an operating valve at said interrupterchamber controlling admission of pressurized gas into said chamber fromthe interior of said insulator column to actuate said contact means,

a valve rod extending upwardly through said insulator column from thebase thereof for actuating said operating valve, electro-responsivecontrol valve means, pneumatically actuated drive means connected tosaid valve rod at the base of said insulator column and which arecontrolled by said control valve means, a second hollow insulator columnupstanding on said gas supply tank, an isolator chamber located at theupper end of and in communication with the interior of said secondinsulator column, pressure gas operated isolator contact means withinsaid isolator chamber, conduit means connecting the interior of saidisolator chamber with the interior of said gas supply tank, apneumo-responsive control valve means located at the base of said secondinsulator column for controlling flow of pressurized gas from said gassupply tank to said isolator contact means for actuation thereof,circuit means connecting said, lead interrupter contact means and saidisolator contact means in series between inlet and outlet terminals ofsaid circuit breaker, a control block on said gas supply tank,electrical transmission means extending from-said control block to saidelectro-responsive control valve means at said first insulator column,pneumatic transmission means extending from said control block to saidpneumo-responsive control valve means at said second insulator column,and auxiliary pneumatic transmission means extending from saidpneumatically actuated drive means for said valve rod at said firstinsulator column to actuate said control valve means at said secondinsulator column in the event of a failure of its normally operativepneumatic supply.

3. In a pressurized gas operated circuit breaker, the combinationcomprising an elongated tank containing a supply of pressurized gas, afirst hollow insulator column upstanding on said gas supply tank andhaving its interior in communication with the interior of said gassupply tank, an interrupter chamber located at the upper end of saidinsulator column, pressure gas operated load interrupter contact meansWithin said interrupter chamber, an operating valve at said interrupterchamber controlling admission of pressurized gas into said chamber fromthe interior of said insulator column to actuate said contact means, avalve rod extending upwardly through said insulator column from the basethereof for actuating said operating valve, electro-responsive controlvalve means, pneumatically actuated drive means connected to said valverod at the base of said insulator column and which are controlled bysaid control'valve means, a second hollow insulator column upstanding onsaid gas supply tank, an isolator chamber located at the upper end ofand in communication with the interior of said second insulator column,pressure gas operated isolator contact means within said isolatorchamber, conduit means connecting the interior of said isolator chamberwith the interior of said gas supply tank, a pneumo-responsive controlvalve means located at the base of said second insulator column forcontrolling flow of pressurized gas from said gas supply tank to saidisolator contact means for actuation thereof, circuit means connectingsaid load interrupter contact means and said isolator contact means inseries between inlet and outlet terminals of said circuit breaker, acontrol block on said gas supply tank, electrical transmission meansextending from said control block to said electroresponsive controlvalve means at said first insulator column, pneumatic transmission meansextending from said control block to said pneumo-responsive controlvalve means at said second insulator column, a first auxiliary pneumatictransmission means extending from said pneumatic transmission means atsaid control block to and for actuating auxiliary pneumo-responsivemeans at said normally electro-responsive control valve means to actuatethe latter in the event of a failure of the normally operativeelectro-r'esponsive means, and a second auxiliary pneumatic transmissionmeans extending from said pneumatically actuated drive means for saidvalve rod at said first insulator column to actuate said control valvemeans at said second insulator column in the event of a failure of itsnormally operative pneumatic supply.

4. In a pressurized gas operated circuit breaker, the combinationcomprising an elongated tank containing a supply of pressurized gas, afirst hollow insulator column upstanding on said gas supply tank andhaving its interior incommunication with the interior of said gas supplytank, an interrupter chamber located at the upper end of said insulatorcolumn, pressure gas operated load interrupter contact means within saidinterrupter chamber, an operating valve at said interrupter chambercontrolling admission of pressurized gas into said chamber from theinterior of said insulator column to actuate said contact means, a valverod extending upwardly through said insulator column from the basethereof for actuating said operating valve, first control valve meanshaving both electrically and pneumatically responsive means foractuating said valve means, pneumatically actuated drive means connectedto said valve rod at the base of said insulator column and which arecontrolled by said first control valve means, a second hollow insulatorcolumn upstanding on said gas supply tank, an isolator chamber locatedat the upper end of and in communication with the interior of saidsecond insulator column, pressure gas operated isolator contact meansWithin said isolator chamber, conduit means connecting the interior ofsaid isolator chamber With the interior of said gas supply tank, asecond control valve means having pneumo-responsive means for actuatingthe same, said second control valve means being located at the base ofsaid second insulator column for controlling fiow of pressurized gasfrom said gas supply tank to said isolator contact means for actuationthereof, a conduit including a control valve therein extending from saidgas supply tank to said pneumo-responsive means for said second controlvalve means, said control valve being provided with both electricallyand pneumatically responsive means for actuating the same, circuit meansconnecting said load interrupter contact means and said isolator contactmeans in series between inlet and outlet terminals of said circuitbreaker, a control block on said gas supply tank, first electricaltransmission means extending from said control block to saidelectrically responsive means on said first control valve means foractuating the latter to open position to actuate said drive means forsaid valve rod, second electrical transmission means to saidelectroresponsive control valve to actuate the latter to open positionthereby to effect flow of pressurized gas through said conduit from saidgas supply tank to said pneumo-responsive means for said second controlvalve means, a first auxiliary pneumatic transmission line extendingfrom said conduit on the discharge side of said control valve therein tosaid pneumatically responsive means for actuating said first controlvalve means in the event of a failure of the normally operativeelectrically responsive means to actuate said first control valve means,and a second auxiliary pneumatic transmission line forconveyingpressurized gas from said pneumatically actuated drive means for saidvalve rod to said pneumatically responsive means for said control valvein said conduit thereby to actuate said confrol valve in the event of afailure of the normally operative electrically responsive means toactuate said control valve.

References Cited by the Examiner UNITED STATES PATENTS 2,213,658 9/ 1940Thommen 200-148 2,708,700 5/1955 Thornmen 200148 2,723,367 11/1955Bockrnan 200l48 X 2,766,354 10/1956 Flurscheim et al 200148 FOREIGNPATENTS 1,052,502 3/ 1959 Germany.

740,792 1 l/ 1955 Great Britain.

KATHLEEN H. CLAFFY, Primary Examiner.

ROBERT S. MACON, Examiner.

P. E. CRAWFORD, Assistant Examiner.

1. IN A PRESSURIZED GAS OPERATED CIRCUIT BREAKER, THE COMBINATIONCOMPRISING AN ELONGATED TANK CONTAINING A SUPPLY OF PRESSURIZED GAS, AFIRST HOLLOW INSULATOR COLUMN UPSTANDING ON SAID GAS SUPPLY TANK ANDHAVING ITS INTERIOR IN COMMUNICATION WITH THE INTERIOR OF SAID GASSUPPLY TANK, AN INTERRUPTER CHAMBER LOCATED AT THE UPPER END OF SAIDINSULATOR COLUMN, PRESSURE GAS OPERATED LOAD INTERRUPTER CONTACT MEANSWITHIN SAID INTERRUPTE CHAMBER, AN OPERATING VALVE AT SAID INTERRUPTERCHAMBER CONTROLLING ADMISSION OF PRESSURIZED GAS INTO SAID CHAMBER FROMTHE INTERIOR OF SAID INSULATOR COLUMN TO ACTUATE SAID CONTACT MEANS, AVALVE ROD EXTENDING UPWARDLY THROUGH SAID INSULATOR COLUMN FROM THE BASETHEREOF FOR ACTUATING SAID OPERATING VALVE, ELECTRO-RESPONSIVE CONTROLVALVE MEANS, PNEUMATICALLY ACTUATED DRIVE MEANS CONNECTED TO SAID VALVEROD AT THE BASE OF SAD INSULATOR COLUMN AND WHICH ARE CONTROLLED BY SAIDCONTROL VALVE MEANS, A SECOND HOLLOW INSULATOR COLUMN UPSTANDING ON SAIDGAS SUPPLY TANK, AN ISOLATOR CHAMBER LOCATED AT THE UPPER END OF AND INCOMMUNICATION WITH THE INTERIOR OF SAID SECOND INSULATOR COLUMN,PRESSURE GAS OPERATED ISOLATOR CONTACT MEANS WITHIN SAID ISOLATORCHAMBER WITH THE INTERIOR CONTACT MEANS WITHIN SAID OF SAID ISOLATORCHAMBER WITH THE INTERIOR OF SAID GAS SUPPLY TANK, A PNEUMO-RESPONSIVECONTROL VALVE MEANS LOCATED AT THE BASE OF SAID SECOND INSULATOR COLUMNFOR CONTROLLING FLOW OF PRESSURIZED GAS FROM SAID GAS SUPPLY TANK TOSAID ISOLATOR CONTACT MEANS FOR ACTUATION THEREOF, CIRCUIT MEANSCONNECTING SAID LOAD INTERRUPTER CONTACT MEANS AND SAID ISOLATOR CONTACTMEANS IN SERIES BETWEEN INLET AND OUTLET TERMINALS OF SAID CIRCUITBREAKER, A CONTROL BLOCK ON SAID GAS SUPPLY TANK, ELECTRICALTRANSMISSION MEANS EXTENDING FROM SAID CONTROL BLOCK TO SAIDELECTRORESPONSIVE CONTROL VALVE MEANS AT SAID FIRST INSULATOR COLUMN,PNEUMATIC TRANSMISSION MEANS EXTENDING FROM SAID CONTROL BLOCK TO SAIDPNEUMO-RESPONSIVE CONTROL VALVE MEANS AT SAID SECOND INSULATOR COLUMNAND AUXILIARY PNEUMATIC TRANSMISSION MEANS EXTENDING FROM SAID PNEUMATICTRANSMISSION MEANS AT SAID CONTROL BLOCK TO AND FOR ACTUATING AUXILIARYPNEUMO-RESPONSIVE MEANS AT SAID NORMALLY ELECTRO-RESPONSIVE CONTROLVALVE MEANS TO ACTUATE THE LATTER IN THE EVENT OF A FAILURE OF THENORMALLY OPERATIVE ELECTRORESPONSIVE MEANS.